This invention relates to the continuous molding of thermoplastic material into a three dimensional sheet from granular form in a continuous process.
The use of vacuum forming on a moving belt has been directed to embossing a preformed sheet of material or to extruding a falling sheet or curtain of material and then embossing.
The present invention is directed to the formation of a sheet of material to be vacuum formed on a continuous moving belt by blending raw granular thermoplastic material and thence extruding such material wherein the granular material such as polyvinyl chloride is fully worked and plasticized. The extruded material is then fed to roller die means which accurately controls the dimension of the hot sheet of thermoplastic material. The conveyor belt which receives the sheet of material is made of flexible material and has a three dimensional mold formed thereon with spaced guides on the respective side portions of the belt so upon pulling of a vacuum on the mold portion of the belt, the sheet material is formed precisely into the shaped mold with clear demarcation lines. An additional roller with moldings thereon may be mounted adjacent to the roller die to assist the formation of the design on the sheet material as it is guided onto the conveyor means for vacuum forming to thereby improve the efficiency and quality of the vacuum forming.